1menu "printk and dmesg options" 2 3config PRINTK_TIME 4 bool "Show timing information on printks" 5 depends on PRINTK 6 help 7 Selecting this option causes time stamps of the printk() 8 messages to be added to the output of the syslog() system 9 call and at the console. 10 11 The timestamp is always recorded internally, and exported 12 to /dev/kmsg. This flag just specifies if the timestamp should 13 be included, not that the timestamp is recorded. 14 15 The behavior is also controlled by the kernel command line 16 parameter printk.time=1. See Documentation/kernel-parameters.txt 17 18config MESSAGE_LOGLEVEL_DEFAULT 19 int "Default message log level (1-7)" 20 range 1 7 21 default "4" 22 help 23 Default log level for printk statements with no specified priority. 24 25 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks 26 that are auditing their logs closely may want to set it to a lower 27 priority. 28 29config BOOT_PRINTK_DELAY 30 bool "Delay each boot printk message by N milliseconds" 31 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 32 help 33 This build option allows you to read kernel boot messages 34 by inserting a short delay after each one. The delay is 35 specified in milliseconds on the kernel command line, 36 using "boot_delay=N". 37 38 It is likely that you would also need to use "lpj=M" to preset 39 the "loops per jiffie" value. 40 See a previous boot log for the "lpj" value to use for your 41 system, and then set "lpj=M" before setting "boot_delay=N". 42 NOTE: Using this option may adversely affect SMP systems. 43 I.e., processors other than the first one may not boot up. 44 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect 45 what it believes to be lockup conditions. 46 47config DYNAMIC_DEBUG 48 bool "Enable dynamic printk() support" 49 default n 50 depends on PRINTK 51 depends on DEBUG_FS 52 help 53 54 Compiles debug level messages into the kernel, which would not 55 otherwise be available at runtime. These messages can then be 56 enabled/disabled based on various levels of scope - per source file, 57 function, module, format string, and line number. This mechanism 58 implicitly compiles in all pr_debug() and dev_dbg() calls, which 59 enlarges the kernel text size by about 2%. 60 61 If a source file is compiled with DEBUG flag set, any 62 pr_debug() calls in it are enabled by default, but can be 63 disabled at runtime as below. Note that DEBUG flag is 64 turned on by many CONFIG_*DEBUG* options. 65 66 Usage: 67 68 Dynamic debugging is controlled via the 'dynamic_debug/control' file, 69 which is contained in the 'debugfs' filesystem. Thus, the debugfs 70 filesystem must first be mounted before making use of this feature. 71 We refer the control file as: <debugfs>/dynamic_debug/control. This 72 file contains a list of the debug statements that can be enabled. The 73 format for each line of the file is: 74 75 filename:lineno [module]function flags format 76 77 filename : source file of the debug statement 78 lineno : line number of the debug statement 79 module : module that contains the debug statement 80 function : function that contains the debug statement 81 flags : '=p' means the line is turned 'on' for printing 82 format : the format used for the debug statement 83 84 From a live system: 85 86 nullarbor:~ # cat <debugfs>/dynamic_debug/control 87 # filename:lineno [module]function flags format 88 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012" 89 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012" 90 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012" 91 92 Example usage: 93 94 // enable the message at line 1603 of file svcsock.c 95 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 96 <debugfs>/dynamic_debug/control 97 98 // enable all the messages in file svcsock.c 99 nullarbor:~ # echo -n 'file svcsock.c +p' > 100 <debugfs>/dynamic_debug/control 101 102 // enable all the messages in the NFS server module 103 nullarbor:~ # echo -n 'module nfsd +p' > 104 <debugfs>/dynamic_debug/control 105 106 // enable all 12 messages in the function svc_process() 107 nullarbor:~ # echo -n 'func svc_process +p' > 108 <debugfs>/dynamic_debug/control 109 110 // disable all 12 messages in the function svc_process() 111 nullarbor:~ # echo -n 'func svc_process -p' > 112 <debugfs>/dynamic_debug/control 113 114 See Documentation/dynamic-debug-howto.txt for additional information. 115 116endmenu # "printk and dmesg options" 117 118menu "Compile-time checks and compiler options" 119 120config DEBUG_INFO 121 bool "Compile the kernel with debug info" 122 depends on DEBUG_KERNEL && !COMPILE_TEST 123 help 124 If you say Y here the resulting kernel image will include 125 debugging info resulting in a larger kernel image. 126 This adds debug symbols to the kernel and modules (gcc -g), and 127 is needed if you intend to use kernel crashdump or binary object 128 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 129 Say Y here only if you plan to debug the kernel. 130 131 If unsure, say N. 132 133config DEBUG_INFO_REDUCED 134 bool "Reduce debugging information" 135 depends on DEBUG_INFO 136 help 137 If you say Y here gcc is instructed to generate less debugging 138 information for structure types. This means that tools that 139 need full debugging information (like kgdb or systemtap) won't 140 be happy. But if you merely need debugging information to 141 resolve line numbers there is no loss. Advantage is that 142 build directory object sizes shrink dramatically over a full 143 DEBUG_INFO build and compile times are reduced too. 144 Only works with newer gcc versions. 145 146config DEBUG_INFO_SPLIT 147 bool "Produce split debuginfo in .dwo files" 148 depends on DEBUG_INFO && !FRV 149 help 150 Generate debug info into separate .dwo files. This significantly 151 reduces the build directory size for builds with DEBUG_INFO, 152 because it stores the information only once on disk in .dwo 153 files instead of multiple times in object files and executables. 154 In addition the debug information is also compressed. 155 156 Requires recent gcc (4.7+) and recent gdb/binutils. 157 Any tool that packages or reads debug information would need 158 to know about the .dwo files and include them. 159 Incompatible with older versions of ccache. 160 161config DEBUG_INFO_DWARF4 162 bool "Generate dwarf4 debuginfo" 163 depends on DEBUG_INFO 164 help 165 Generate dwarf4 debug info. This requires recent versions 166 of gcc and gdb. It makes the debug information larger. 167 But it significantly improves the success of resolving 168 variables in gdb on optimized code. 169 170config GDB_SCRIPTS 171 bool "Provide GDB scripts for kernel debugging" 172 depends on DEBUG_INFO 173 help 174 This creates the required links to GDB helper scripts in the 175 build directory. If you load vmlinux into gdb, the helper 176 scripts will be automatically imported by gdb as well, and 177 additional functions are available to analyze a Linux kernel 178 instance. See Documentation/gdb-kernel-debugging.txt for further 179 details. 180 181config ENABLE_WARN_DEPRECATED 182 bool "Enable __deprecated logic" 183 default y 184 help 185 Enable the __deprecated logic in the kernel build. 186 Disable this to suppress the "warning: 'foo' is deprecated 187 (declared at kernel/power/somefile.c:1234)" messages. 188 189config ENABLE_MUST_CHECK 190 bool "Enable __must_check logic" 191 default y 192 help 193 Enable the __must_check logic in the kernel build. Disable this to 194 suppress the "warning: ignoring return value of 'foo', declared with 195 attribute warn_unused_result" messages. 196 197config FRAME_WARN 198 int "Warn for stack frames larger than (needs gcc 4.4)" 199 range 0 8192 200 default 2048 if GCC_PLUGIN_LATENT_ENTROPY 201 default 1024 if !64BIT 202 default 2048 if 64BIT 203 help 204 Tell gcc to warn at build time for stack frames larger than this. 205 Setting this too low will cause a lot of warnings. 206 Setting it to 0 disables the warning. 207 Requires gcc 4.4 208 209config STRIP_ASM_SYMS 210 bool "Strip assembler-generated symbols during link" 211 default n 212 help 213 Strip internal assembler-generated symbols during a link (symbols 214 that look like '.Lxxx') so they don't pollute the output of 215 get_wchan() and suchlike. 216 217config READABLE_ASM 218 bool "Generate readable assembler code" 219 depends on DEBUG_KERNEL 220 help 221 Disable some compiler optimizations that tend to generate human unreadable 222 assembler output. This may make the kernel slightly slower, but it helps 223 to keep kernel developers who have to stare a lot at assembler listings 224 sane. 225 226config UNUSED_SYMBOLS 227 bool "Enable unused/obsolete exported symbols" 228 default y if X86 229 help 230 Unused but exported symbols make the kernel needlessly bigger. For 231 that reason most of these unused exports will soon be removed. This 232 option is provided temporarily to provide a transition period in case 233 some external kernel module needs one of these symbols anyway. If you 234 encounter such a case in your module, consider if you are actually 235 using the right API. (rationale: since nobody in the kernel is using 236 this in a module, there is a pretty good chance it's actually the 237 wrong interface to use). If you really need the symbol, please send a 238 mail to the linux kernel mailing list mentioning the symbol and why 239 you really need it, and what the merge plan to the mainline kernel for 240 your module is. 241 242config PAGE_OWNER 243 bool "Track page owner" 244 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT 245 select DEBUG_FS 246 select STACKTRACE 247 select STACKDEPOT 248 select PAGE_EXTENSION 249 help 250 This keeps track of what call chain is the owner of a page, may 251 help to find bare alloc_page(s) leaks. Even if you include this 252 feature on your build, it is disabled in default. You should pass 253 "page_owner=on" to boot parameter in order to enable it. Eats 254 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c 255 for user-space helper. 256 257 If unsure, say N. 258 259config DEBUG_FS 260 bool "Debug Filesystem" 261 select SRCU 262 help 263 debugfs is a virtual file system that kernel developers use to put 264 debugging files into. Enable this option to be able to read and 265 write to these files. 266 267 For detailed documentation on the debugfs API, see 268 Documentation/DocBook/filesystems. 269 270 If unsure, say N. 271 272config HEADERS_CHECK 273 bool "Run 'make headers_check' when building vmlinux" 274 depends on !UML 275 help 276 This option will extract the user-visible kernel headers whenever 277 building the kernel, and will run basic sanity checks on them to 278 ensure that exported files do not attempt to include files which 279 were not exported, etc. 280 281 If you're making modifications to header files which are 282 relevant for userspace, say 'Y', and check the headers 283 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 284 your build tree), to make sure they're suitable. 285 286config DEBUG_SECTION_MISMATCH 287 bool "Enable full Section mismatch analysis" 288 help 289 The section mismatch analysis checks if there are illegal 290 references from one section to another section. 291 During linktime or runtime, some sections are dropped; 292 any use of code/data previously in these sections would 293 most likely result in an oops. 294 In the code, functions and variables are annotated with 295 __init,, etc. (see the full list in include/linux/init.h), 296 which results in the code/data being placed in specific sections. 297 The section mismatch analysis is always performed after a full 298 kernel build, and enabling this option causes the following 299 additional steps to occur: 300 - Add the option -fno-inline-functions-called-once to gcc commands. 301 When inlining a function annotated with __init in a non-init 302 function, we would lose the section information and thus 303 the analysis would not catch the illegal reference. 304 This option tells gcc to inline less (but it does result in 305 a larger kernel). 306 - Run the section mismatch analysis for each module/built-in.o file. 307 When we run the section mismatch analysis on vmlinux.o, we 308 lose valuable information about where the mismatch was 309 introduced. 310 Running the analysis for each module/built-in.o file 311 tells where the mismatch happens much closer to the 312 source. The drawback is that the same mismatch is 313 reported at least twice. 314 - Enable verbose reporting from modpost in order to help resolve 315 the section mismatches that are reported. 316 317config SECTION_MISMATCH_WARN_ONLY 318 bool "Make section mismatch errors non-fatal" 319 default y 320 help 321 If you say N here, the build process will fail if there are any 322 section mismatch, instead of just throwing warnings. 323 324 If unsure, say Y. 325 326# 327# Select this config option from the architecture Kconfig, if it 328# is preferred to always offer frame pointers as a config 329# option on the architecture (regardless of KERNEL_DEBUG): 330# 331config ARCH_WANT_FRAME_POINTERS 332 bool 333 help 334 335config FRAME_POINTER 336 bool "Compile the kernel with frame pointers" 337 depends on DEBUG_KERNEL && \ 338 (CRIS || M68K || FRV || UML || \ 339 AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \ 340 ARCH_WANT_FRAME_POINTERS 341 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 342 help 343 If you say Y here the resulting kernel image will be slightly 344 larger and slower, but it gives very useful debugging information 345 in case of kernel bugs. (precise oopses/stacktraces/warnings) 346 347config STACK_VALIDATION 348 bool "Compile-time stack metadata validation" 349 depends on HAVE_STACK_VALIDATION 350 default n 351 help 352 Add compile-time checks to validate stack metadata, including frame 353 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure 354 that runtime stack traces are more reliable. 355 356 For more information, see 357 tools/objtool/Documentation/stack-validation.txt. 358 359config DEBUG_FORCE_WEAK_PER_CPU 360 bool "Force weak per-cpu definitions" 361 depends on DEBUG_KERNEL 362 help 363 s390 and alpha require percpu variables in modules to be 364 defined weak to work around addressing range issue which 365 puts the following two restrictions on percpu variable 366 definitions. 367 368 1. percpu symbols must be unique whether static or not 369 2. percpu variables can't be defined inside a function 370 371 To ensure that generic code follows the above rules, this 372 option forces all percpu variables to be defined as weak. 373 374endmenu # "Compiler options" 375 376config MAGIC_SYSRQ 377 bool "Magic SysRq key" 378 depends on !UML 379 help 380 If you say Y here, you will have some control over the system even 381 if the system crashes for example during kernel debugging (e.g., you 382 will be able to flush the buffer cache to disk, reboot the system 383 immediately or dump some status information). This is accomplished 384 by pressing various keys while holding SysRq (Alt+PrintScreen). It 385 also works on a serial console (on PC hardware at least), if you 386 send a BREAK and then within 5 seconds a command keypress. The 387 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y 388 unless you really know what this hack does. 389 390config MAGIC_SYSRQ_DEFAULT_ENABLE 391 hex "Enable magic SysRq key functions by default" 392 depends on MAGIC_SYSRQ 393 default 0x1 394 help 395 Specifies which SysRq key functions are enabled by default. 396 This may be set to 1 or 0 to enable or disable them all, or 397 to a bitmask as described in Documentation/sysrq.txt. 398 399config DEBUG_KERNEL 400 bool "Kernel debugging" 401 help 402 Say Y here if you are developing drivers or trying to debug and 403 identify kernel problems. 404 405menu "Memory Debugging" 406 407source mm/Kconfig.debug 408 409config DEBUG_OBJECTS 410 bool "Debug object operations" 411 depends on DEBUG_KERNEL 412 help 413 If you say Y here, additional code will be inserted into the 414 kernel to track the life time of various objects and validate 415 the operations on those objects. 416 417config DEBUG_OBJECTS_SELFTEST 418 bool "Debug objects selftest" 419 depends on DEBUG_OBJECTS 420 help 421 This enables the selftest of the object debug code. 422 423config DEBUG_OBJECTS_FREE 424 bool "Debug objects in freed memory" 425 depends on DEBUG_OBJECTS 426 help 427 This enables checks whether a k/v free operation frees an area 428 which contains an object which has not been deactivated 429 properly. This can make kmalloc/kfree-intensive workloads 430 much slower. 431 432config DEBUG_OBJECTS_TIMERS 433 bool "Debug timer objects" 434 depends on DEBUG_OBJECTS 435 help 436 If you say Y here, additional code will be inserted into the 437 timer routines to track the life time of timer objects and 438 validate the timer operations. 439 440config DEBUG_OBJECTS_WORK 441 bool "Debug work objects" 442 depends on DEBUG_OBJECTS 443 help 444 If you say Y here, additional code will be inserted into the 445 work queue routines to track the life time of work objects and 446 validate the work operations. 447 448config DEBUG_OBJECTS_RCU_HEAD 449 bool "Debug RCU callbacks objects" 450 depends on DEBUG_OBJECTS 451 help 452 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 453 454config DEBUG_OBJECTS_PERCPU_COUNTER 455 bool "Debug percpu counter objects" 456 depends on DEBUG_OBJECTS 457 help 458 If you say Y here, additional code will be inserted into the 459 percpu counter routines to track the life time of percpu counter 460 objects and validate the percpu counter operations. 461 462config DEBUG_OBJECTS_ENABLE_DEFAULT 463 int "debug_objects bootup default value (0-1)" 464 range 0 1 465 default "1" 466 depends on DEBUG_OBJECTS 467 help 468 Debug objects boot parameter default value 469 470config DEBUG_SLAB 471 bool "Debug slab memory allocations" 472 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 473 help 474 Say Y here to have the kernel do limited verification on memory 475 allocation as well as poisoning memory on free to catch use of freed 476 memory. This can make kmalloc/kfree-intensive workloads much slower. 477 478config DEBUG_SLAB_LEAK 479 bool "Memory leak debugging" 480 depends on DEBUG_SLAB 481 482config SLUB_DEBUG_ON 483 bool "SLUB debugging on by default" 484 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 485 default n 486 help 487 Boot with debugging on by default. SLUB boots by default with 488 the runtime debug capabilities switched off. Enabling this is 489 equivalent to specifying the "slub_debug" parameter on boot. 490 There is no support for more fine grained debug control like 491 possible with slub_debug=xxx. SLUB debugging may be switched 492 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 493 "slub_debug=-". 494 495config SLUB_STATS 496 default n 497 bool "Enable SLUB performance statistics" 498 depends on SLUB && SYSFS 499 help 500 SLUB statistics are useful to debug SLUBs allocation behavior in 501 order find ways to optimize the allocator. This should never be 502 enabled for production use since keeping statistics slows down 503 the allocator by a few percentage points. The slabinfo command 504 supports the determination of the most active slabs to figure 505 out which slabs are relevant to a particular load. 506 Try running: slabinfo -DA 507 508config HAVE_DEBUG_KMEMLEAK 509 bool 510 511config DEBUG_KMEMLEAK 512 bool "Kernel memory leak detector" 513 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK 514 select DEBUG_FS 515 select STACKTRACE if STACKTRACE_SUPPORT 516 select KALLSYMS 517 select CRC32 518 help 519 Say Y here if you want to enable the memory leak 520 detector. The memory allocation/freeing is traced in a way 521 similar to the Boehm's conservative garbage collector, the 522 difference being that the orphan objects are not freed but 523 only shown in /sys/kernel/debug/kmemleak. Enabling this 524 feature will introduce an overhead to memory 525 allocations. See Documentation/kmemleak.txt for more 526 details. 527 528 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 529 of finding leaks due to the slab objects poisoning. 530 531 In order to access the kmemleak file, debugfs needs to be 532 mounted (usually at /sys/kernel/debug). 533 534config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 535 int "Maximum kmemleak early log entries" 536 depends on DEBUG_KMEMLEAK 537 range 200 40000 538 default 400 539 help 540 Kmemleak must track all the memory allocations to avoid 541 reporting false positives. Since memory may be allocated or 542 freed before kmemleak is initialised, an early log buffer is 543 used to store these actions. If kmemleak reports "early log 544 buffer exceeded", please increase this value. 545 546config DEBUG_KMEMLEAK_TEST 547 tristate "Simple test for the kernel memory leak detector" 548 depends on DEBUG_KMEMLEAK && m 549 help 550 This option enables a module that explicitly leaks memory. 551 552 If unsure, say N. 553 554config DEBUG_KMEMLEAK_DEFAULT_OFF 555 bool "Default kmemleak to off" 556 depends on DEBUG_KMEMLEAK 557 help 558 Say Y here to disable kmemleak by default. It can then be enabled 559 on the command line via kmemleak=on. 560 561config DEBUG_STACK_USAGE 562 bool "Stack utilization instrumentation" 563 depends on DEBUG_KERNEL && !IA64 564 help 565 Enables the display of the minimum amount of free stack which each 566 task has ever had available in the sysrq-T and sysrq-P debug output. 567 568 This option will slow down process creation somewhat. 569 570config DEBUG_VM 571 bool "Debug VM" 572 depends on DEBUG_KERNEL 573 help 574 Enable this to turn on extended checks in the virtual-memory system 575 that may impact performance. 576 577 If unsure, say N. 578 579config DEBUG_VM_VMACACHE 580 bool "Debug VMA caching" 581 depends on DEBUG_VM 582 help 583 Enable this to turn on VMA caching debug information. Doing so 584 can cause significant overhead, so only enable it in non-production 585 environments. 586 587 If unsure, say N. 588 589config DEBUG_VM_RB 590 bool "Debug VM red-black trees" 591 depends on DEBUG_VM 592 help 593 Enable VM red-black tree debugging information and extra validations. 594 595 If unsure, say N. 596 597config DEBUG_VM_PGFLAGS 598 bool "Debug page-flags operations" 599 depends on DEBUG_VM 600 help 601 Enables extra validation on page flags operations. 602 603 If unsure, say N. 604 605config DEBUG_VIRTUAL 606 bool "Debug VM translations" 607 depends on DEBUG_KERNEL && X86 608 help 609 Enable some costly sanity checks in virtual to page code. This can 610 catch mistakes with virt_to_page() and friends. 611 612 If unsure, say N. 613 614config DEBUG_NOMMU_REGIONS 615 bool "Debug the global anon/private NOMMU mapping region tree" 616 depends on DEBUG_KERNEL && !MMU 617 help 618 This option causes the global tree of anonymous and private mapping 619 regions to be regularly checked for invalid topology. 620 621config DEBUG_MEMORY_INIT 622 bool "Debug memory initialisation" if EXPERT 623 default !EXPERT 624 help 625 Enable this for additional checks during memory initialisation. 626 The sanity checks verify aspects of the VM such as the memory model 627 and other information provided by the architecture. Verbose 628 information will be printed at KERN_DEBUG loglevel depending 629 on the mminit_loglevel= command-line option. 630 631 If unsure, say Y 632 633config MEMORY_NOTIFIER_ERROR_INJECT 634 tristate "Memory hotplug notifier error injection module" 635 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 636 help 637 This option provides the ability to inject artificial errors to 638 memory hotplug notifier chain callbacks. It is controlled through 639 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 640 641 If the notifier call chain should be failed with some events 642 notified, write the error code to "actions/<notifier event>/error". 643 644 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 645 646 # cd /sys/kernel/debug/notifier-error-inject/memory 647 # echo -12 > actions/MEM_GOING_OFFLINE/error 648 # echo offline > /sys/devices/system/memory/memoryXXX/state 649 bash: echo: write error: Cannot allocate memory 650 651 To compile this code as a module, choose M here: the module will 652 be called memory-notifier-error-inject. 653 654 If unsure, say N. 655 656config DEBUG_PER_CPU_MAPS 657 bool "Debug access to per_cpu maps" 658 depends on DEBUG_KERNEL 659 depends on SMP 660 help 661 Say Y to verify that the per_cpu map being accessed has 662 been set up. This adds a fair amount of code to kernel memory 663 and decreases performance. 664 665 Say N if unsure. 666 667config DEBUG_HIGHMEM 668 bool "Highmem debugging" 669 depends on DEBUG_KERNEL && HIGHMEM 670 help 671 This option enables additional error checking for high memory 672 systems. Disable for production systems. 673 674config HAVE_DEBUG_STACKOVERFLOW 675 bool 676 677config DEBUG_STACKOVERFLOW 678 bool "Check for stack overflows" 679 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW 680 ---help--- 681 Say Y here if you want to check for overflows of kernel, IRQ 682 and exception stacks (if your architecture uses them). This 683 option will show detailed messages if free stack space drops 684 below a certain limit. 685 686 These kinds of bugs usually occur when call-chains in the 687 kernel get too deep, especially when interrupts are 688 involved. 689 690 Use this in cases where you see apparently random memory 691 corruption, especially if it appears in 'struct thread_info' 692 693 If in doubt, say "N". 694 695source "lib/Kconfig.kmemcheck" 696 697source "lib/Kconfig.kasan" 698 699endmenu # "Memory Debugging" 700 701config ARCH_HAS_KCOV 702 bool 703 help 704 KCOV does not have any arch-specific code, but currently it is enabled 705 only for x86_64. KCOV requires testing on other archs, and most likely 706 disabling of instrumentation for some early boot code. 707 708config KCOV 709 bool "Code coverage for fuzzing" 710 depends on ARCH_HAS_KCOV 711 select DEBUG_FS 712 select GCC_PLUGINS if !COMPILE_TEST 713 select GCC_PLUGIN_SANCOV if !COMPILE_TEST 714 help 715 KCOV exposes kernel code coverage information in a form suitable 716 for coverage-guided fuzzing (randomized testing). 717 718 If RANDOMIZE_BASE is enabled, PC values will not be stable across 719 different machines and across reboots. If you need stable PC values, 720 disable RANDOMIZE_BASE. 721 722 For more details, see Documentation/kcov.txt. 723 724config KCOV_INSTRUMENT_ALL 725 bool "Instrument all code by default" 726 depends on KCOV 727 default y if KCOV 728 help 729 If you are doing generic system call fuzzing (like e.g. syzkaller), 730 then you will want to instrument the whole kernel and you should 731 say y here. If you are doing more targeted fuzzing (like e.g. 732 filesystem fuzzing with AFL) then you will want to enable coverage 733 for more specific subsets of files, and should say n here. 734 735config DEBUG_SHIRQ 736 bool "Debug shared IRQ handlers" 737 depends on DEBUG_KERNEL 738 help 739 Enable this to generate a spurious interrupt as soon as a shared 740 interrupt handler is registered, and just before one is deregistered. 741 Drivers ought to be able to handle interrupts coming in at those 742 points; some don't and need to be caught. 743 744menu "Debug Lockups and Hangs" 745 746config LOCKUP_DETECTOR 747 bool "Detect Hard and Soft Lockups" 748 depends on DEBUG_KERNEL && !S390 749 help 750 Say Y here to enable the kernel to act as a watchdog to detect 751 hard and soft lockups. 752 753 Softlockups are bugs that cause the kernel to loop in kernel 754 mode for more than 20 seconds, without giving other tasks a 755 chance to run. The current stack trace is displayed upon 756 detection and the system will stay locked up. 757 758 Hardlockups are bugs that cause the CPU to loop in kernel mode 759 for more than 10 seconds, without letting other interrupts have a 760 chance to run. The current stack trace is displayed upon detection 761 and the system will stay locked up. 762 763 The overhead should be minimal. A periodic hrtimer runs to 764 generate interrupts and kick the watchdog task every 4 seconds. 765 An NMI is generated every 10 seconds or so to check for hardlockups. 766 767 The frequency of hrtimer and NMI events and the soft and hard lockup 768 thresholds can be controlled through the sysctl watchdog_thresh. 769 770config HARDLOCKUP_DETECTOR 771 def_bool y 772 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG 773 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI 774 775config BOOTPARAM_HARDLOCKUP_PANIC 776 bool "Panic (Reboot) On Hard Lockups" 777 depends on HARDLOCKUP_DETECTOR 778 help 779 Say Y here to enable the kernel to panic on "hard lockups", 780 which are bugs that cause the kernel to loop in kernel 781 mode with interrupts disabled for more than 10 seconds (configurable 782 using the watchdog_thresh sysctl). 783 784 Say N if unsure. 785 786config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 787 int 788 depends on HARDLOCKUP_DETECTOR 789 range 0 1 790 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 791 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 792 793config BOOTPARAM_SOFTLOCKUP_PANIC 794 bool "Panic (Reboot) On Soft Lockups" 795 depends on LOCKUP_DETECTOR 796 help 797 Say Y here to enable the kernel to panic on "soft lockups", 798 which are bugs that cause the kernel to loop in kernel 799 mode for more than 20 seconds (configurable using the watchdog_thresh 800 sysctl), without giving other tasks a chance to run. 801 802 The panic can be used in combination with panic_timeout, 803 to cause the system to reboot automatically after a 804 lockup has been detected. This feature is useful for 805 high-availability systems that have uptime guarantees and 806 where a lockup must be resolved ASAP. 807 808 Say N if unsure. 809 810config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 811 int 812 depends on LOCKUP_DETECTOR 813 range 0 1 814 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 815 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 816 817config DETECT_HUNG_TASK 818 bool "Detect Hung Tasks" 819 depends on DEBUG_KERNEL 820 default LOCKUP_DETECTOR 821 help 822 Say Y here to enable the kernel to detect "hung tasks", 823 which are bugs that cause the task to be stuck in 824 uninterruptible "D" state indefinitely. 825 826 When a hung task is detected, the kernel will print the 827 current stack trace (which you should report), but the 828 task will stay in uninterruptible state. If lockdep is 829 enabled then all held locks will also be reported. This 830 feature has negligible overhead. 831 832config DEFAULT_HUNG_TASK_TIMEOUT 833 int "Default timeout for hung task detection (in seconds)" 834 depends on DETECT_HUNG_TASK 835 default 120 836 help 837 This option controls the default timeout (in seconds) used 838 to determine when a task has become non-responsive and should 839 be considered hung. 840 841 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 842 sysctl or by writing a value to 843 /proc/sys/kernel/hung_task_timeout_secs. 844 845 A timeout of 0 disables the check. The default is two minutes. 846 Keeping the default should be fine in most cases. 847 848config BOOTPARAM_HUNG_TASK_PANIC 849 bool "Panic (Reboot) On Hung Tasks" 850 depends on DETECT_HUNG_TASK 851 help 852 Say Y here to enable the kernel to panic on "hung tasks", 853 which are bugs that cause the kernel to leave a task stuck 854 in uninterruptible "D" state. 855 856 The panic can be used in combination with panic_timeout, 857 to cause the system to reboot automatically after a 858 hung task has been detected. This feature is useful for 859 high-availability systems that have uptime guarantees and 860 where a hung tasks must be resolved ASAP. 861 862 Say N if unsure. 863 864config BOOTPARAM_HUNG_TASK_PANIC_VALUE 865 int 866 depends on DETECT_HUNG_TASK 867 range 0 1 868 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 869 default 1 if BOOTPARAM_HUNG_TASK_PANIC 870 871config WQ_WATCHDOG 872 bool "Detect Workqueue Stalls" 873 depends on DEBUG_KERNEL 874 help 875 Say Y here to enable stall detection on workqueues. If a 876 worker pool doesn't make forward progress on a pending work 877 item for over a given amount of time, 30s by default, a 878 warning message is printed along with dump of workqueue 879 state. This can be configured through kernel parameter 880 "workqueue.watchdog_thresh" and its sysfs counterpart. 881 882endmenu # "Debug lockups and hangs" 883 884config PANIC_ON_OOPS 885 bool "Panic on Oops" 886 help 887 Say Y here to enable the kernel to panic when it oopses. This 888 has the same effect as setting oops=panic on the kernel command 889 line. 890 891 This feature is useful to ensure that the kernel does not do 892 anything erroneous after an oops which could result in data 893 corruption or other issues. 894 895 Say N if unsure. 896 897config PANIC_ON_OOPS_VALUE 898 int 899 range 0 1 900 default 0 if !PANIC_ON_OOPS 901 default 1 if PANIC_ON_OOPS 902 903config PANIC_TIMEOUT 904 int "panic timeout" 905 default 0 906 help 907 Set the timeout value (in seconds) until a reboot occurs when the 908 the kernel panics. If n = 0, then we wait forever. A timeout 909 value n > 0 will wait n seconds before rebooting, while a timeout 910 value n < 0 will reboot immediately. 911 912config SCHED_DEBUG 913 bool "Collect scheduler debugging info" 914 depends on DEBUG_KERNEL && PROC_FS 915 default y 916 help 917 If you say Y here, the /proc/sched_debug file will be provided 918 that can help debug the scheduler. The runtime overhead of this 919 option is minimal. 920 921config SCHED_INFO 922 bool 923 default n 924 925config PANIC_ON_RT_THROTTLING 926 bool "Panic on RT throttling" 927 help 928 Say Y here to enable the kernel to panic when a realtime 929 runqueue is throttled. This may be useful for detecting 930 and debugging RT throttling issues. 931 932 Say N if unsure. 933 934config SCHEDSTATS 935 bool "Collect scheduler statistics" 936 depends on DEBUG_KERNEL && PROC_FS 937 select SCHED_INFO 938 help 939 If you say Y here, additional code will be inserted into the 940 scheduler and related routines to collect statistics about 941 scheduler behavior and provide them in /proc/schedstat. These 942 stats may be useful for both tuning and debugging the scheduler 943 If you aren't debugging the scheduler or trying to tune a specific 944 application, you can say N to avoid the very slight overhead 945 this adds. 946 947config SCHED_STACK_END_CHECK 948 bool "Detect stack corruption on calls to schedule()" 949 depends on DEBUG_KERNEL 950 default n 951 help 952 This option checks for a stack overrun on calls to schedule(). 953 If the stack end location is found to be over written always panic as 954 the content of the corrupted region can no longer be trusted. 955 This is to ensure no erroneous behaviour occurs which could result in 956 data corruption or a sporadic crash at a later stage once the region 957 is examined. The runtime overhead introduced is minimal. 958 959config DEBUG_TIMEKEEPING 960 bool "Enable extra timekeeping sanity checking" 961 help 962 This option will enable additional timekeeping sanity checks 963 which may be helpful when diagnosing issues where timekeeping 964 problems are suspected. 965 966 This may include checks in the timekeeping hotpaths, so this 967 option may have a (very small) performance impact to some 968 workloads. 969 970 If unsure, say N. 971 972config TIMER_STATS 973 bool "Collect kernel timers statistics" 974 depends on DEBUG_KERNEL && PROC_FS 975 help 976 If you say Y here, additional code will be inserted into the 977 timer routines to collect statistics about kernel timers being 978 reprogrammed. The statistics can be read from /proc/timer_stats. 979 The statistics collection is started by writing 1 to /proc/timer_stats, 980 writing 0 stops it. This feature is useful to collect information 981 about timer usage patterns in kernel and userspace. This feature 982 is lightweight if enabled in the kernel config but not activated 983 (it defaults to deactivated on bootup and will only be activated 984 if some application like powertop activates it explicitly). 985 986config DEBUG_PREEMPT 987 bool "Debug preemptible kernel" 988 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 989 default y 990 help 991 If you say Y here then the kernel will use a debug variant of the 992 commonly used smp_processor_id() function and will print warnings 993 if kernel code uses it in a preemption-unsafe way. Also, the kernel 994 will detect preemption count underflows. 995 996menu "Lock Debugging (spinlocks, mutexes, etc...)" 997 998config DEBUG_RT_MUTEXES 999 bool "RT Mutex debugging, deadlock detection" 1000 depends on DEBUG_KERNEL && RT_MUTEXES 1001 help 1002 This allows rt mutex semantics violations and rt mutex related 1003 deadlocks (lockups) to be detected and reported automatically. 1004 1005config DEBUG_SPINLOCK 1006 bool "Spinlock and rw-lock debugging: basic checks" 1007 depends on DEBUG_KERNEL 1008 select UNINLINE_SPIN_UNLOCK 1009 help 1010 Say Y here and build SMP to catch missing spinlock initialization 1011 and certain other kinds of spinlock errors commonly made. This is 1012 best used in conjunction with the NMI watchdog so that spinlock 1013 deadlocks are also debuggable. 1014 1015config DEBUG_MUTEXES 1016 bool "Mutex debugging: basic checks" 1017 depends on DEBUG_KERNEL 1018 help 1019 This feature allows mutex semantics violations to be detected and 1020 reported. 1021 1022config DEBUG_WW_MUTEX_SLOWPATH 1023 bool "Wait/wound mutex debugging: Slowpath testing" 1024 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1025 select DEBUG_LOCK_ALLOC 1026 select DEBUG_SPINLOCK 1027 select DEBUG_MUTEXES 1028 help 1029 This feature enables slowpath testing for w/w mutex users by 1030 injecting additional -EDEADLK wound/backoff cases. Together with 1031 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this 1032 will test all possible w/w mutex interface abuse with the 1033 exception of simply not acquiring all the required locks. 1034 Note that this feature can introduce significant overhead, so 1035 it really should not be enabled in a production or distro kernel, 1036 even a debug kernel. If you are a driver writer, enable it. If 1037 you are a distro, do not. 1038 1039config DEBUG_LOCK_ALLOC 1040 bool "Lock debugging: detect incorrect freeing of live locks" 1041 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1042 select DEBUG_SPINLOCK 1043 select DEBUG_MUTEXES 1044 select LOCKDEP 1045 help 1046 This feature will check whether any held lock (spinlock, rwlock, 1047 mutex or rwsem) is incorrectly freed by the kernel, via any of the 1048 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 1049 vfree(), etc.), whether a live lock is incorrectly reinitialized via 1050 spin_lock_init()/mutex_init()/etc., or whether there is any lock 1051 held during task exit. 1052 1053config PROVE_LOCKING 1054 bool "Lock debugging: prove locking correctness" 1055 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1056 select LOCKDEP 1057 select DEBUG_SPINLOCK 1058 select DEBUG_MUTEXES 1059 select DEBUG_LOCK_ALLOC 1060 select TRACE_IRQFLAGS 1061 default n 1062 help 1063 This feature enables the kernel to prove that all locking 1064 that occurs in the kernel runtime is mathematically 1065 correct: that under no circumstance could an arbitrary (and 1066 not yet triggered) combination of observed locking 1067 sequences (on an arbitrary number of CPUs, running an 1068 arbitrary number of tasks and interrupt contexts) cause a 1069 deadlock. 1070 1071 In short, this feature enables the kernel to report locking 1072 related deadlocks before they actually occur. 1073 1074 The proof does not depend on how hard and complex a 1075 deadlock scenario would be to trigger: how many 1076 participant CPUs, tasks and irq-contexts would be needed 1077 for it to trigger. The proof also does not depend on 1078 timing: if a race and a resulting deadlock is possible 1079 theoretically (no matter how unlikely the race scenario 1080 is), it will be proven so and will immediately be 1081 reported by the kernel (once the event is observed that 1082 makes the deadlock theoretically possible). 1083 1084 If a deadlock is impossible (i.e. the locking rules, as 1085 observed by the kernel, are mathematically correct), the 1086 kernel reports nothing. 1087 1088 NOTE: this feature can also be enabled for rwlocks, mutexes 1089 and rwsems - in which case all dependencies between these 1090 different locking variants are observed and mapped too, and 1091 the proof of observed correctness is also maintained for an 1092 arbitrary combination of these separate locking variants. 1093 1094 For more details, see Documentation/locking/lockdep-design.txt. 1095 1096config PROVE_LOCKING_SMALL 1097 bool 1098 1099config LOCKDEP 1100 bool 1101 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1102 select STACKTRACE 1103 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE 1104 select KALLSYMS 1105 select KALLSYMS_ALL 1106 1107config LOCK_STAT 1108 bool "Lock usage statistics" 1109 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1110 select LOCKDEP 1111 select DEBUG_SPINLOCK 1112 select DEBUG_MUTEXES 1113 select DEBUG_LOCK_ALLOC 1114 default n 1115 help 1116 This feature enables tracking lock contention points 1117 1118 For more details, see Documentation/locking/lockstat.txt 1119 1120 This also enables lock events required by "perf lock", 1121 subcommand of perf. 1122 If you want to use "perf lock", you also need to turn on 1123 CONFIG_EVENT_TRACING. 1124 1125 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 1126 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 1127 1128config DEBUG_LOCKDEP 1129 bool "Lock dependency engine debugging" 1130 depends on DEBUG_KERNEL && LOCKDEP 1131 help 1132 If you say Y here, the lock dependency engine will do 1133 additional runtime checks to debug itself, at the price 1134 of more runtime overhead. 1135 1136config DEBUG_ATOMIC_SLEEP 1137 bool "Sleep inside atomic section checking" 1138 select PREEMPT_COUNT 1139 depends on DEBUG_KERNEL 1140 help 1141 If you say Y here, various routines which may sleep will become very 1142 noisy if they are called inside atomic sections: when a spinlock is 1143 held, inside an rcu read side critical section, inside preempt disabled 1144 sections, inside an interrupt, etc... 1145 1146config DEBUG_LOCKING_API_SELFTESTS 1147 bool "Locking API boot-time self-tests" 1148 depends on DEBUG_KERNEL 1149 help 1150 Say Y here if you want the kernel to run a short self-test during 1151 bootup. The self-test checks whether common types of locking bugs 1152 are detected by debugging mechanisms or not. (if you disable 1153 lock debugging then those bugs wont be detected of course.) 1154 The following locking APIs are covered: spinlocks, rwlocks, 1155 mutexes and rwsems. 1156 1157config LOCK_TORTURE_TEST 1158 tristate "torture tests for locking" 1159 depends on DEBUG_KERNEL 1160 select TORTURE_TEST 1161 default n 1162 help 1163 This option provides a kernel module that runs torture tests 1164 on kernel locking primitives. The kernel module may be built 1165 after the fact on the running kernel to be tested, if desired. 1166 1167 Say Y here if you want kernel locking-primitive torture tests 1168 to be built into the kernel. 1169 Say M if you want these torture tests to build as a module. 1170 Say N if you are unsure. 1171 1172endmenu # lock debugging 1173 1174config TRACE_IRQFLAGS 1175 bool 1176 help 1177 Enables hooks to interrupt enabling and disabling for 1178 either tracing or lock debugging. 1179 1180config STACKTRACE 1181 bool "Stack backtrace support" 1182 depends on STACKTRACE_SUPPORT 1183 help 1184 This option causes the kernel to create a /proc/pid/stack for 1185 every process, showing its current stack trace. 1186 It is also used by various kernel debugging features that require 1187 stack trace generation. 1188 1189config DEBUG_KOBJECT 1190 bool "kobject debugging" 1191 depends on DEBUG_KERNEL 1192 help 1193 If you say Y here, some extra kobject debugging messages will be sent 1194 to the syslog. 1195 1196config DEBUG_KOBJECT_RELEASE 1197 bool "kobject release debugging" 1198 depends on DEBUG_OBJECTS_TIMERS 1199 help 1200 kobjects are reference counted objects. This means that their 1201 last reference count put is not predictable, and the kobject can 1202 live on past the point at which a driver decides to drop it's 1203 initial reference to the kobject gained on allocation. An 1204 example of this would be a struct device which has just been 1205 unregistered. 1206 1207 However, some buggy drivers assume that after such an operation, 1208 the memory backing the kobject can be immediately freed. This 1209 goes completely against the principles of a refcounted object. 1210 1211 If you say Y here, the kernel will delay the release of kobjects 1212 on the last reference count to improve the visibility of this 1213 kind of kobject release bug. 1214 1215config HAVE_DEBUG_BUGVERBOSE 1216 bool 1217 1218config DEBUG_BUGVERBOSE 1219 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 1220 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 1221 default y 1222 help 1223 Say Y here to make BUG() panics output the file name and line number 1224 of the BUG call as well as the EIP and oops trace. This aids 1225 debugging but costs about 70-100K of memory. 1226 1227config DEBUG_LIST 1228 bool "Debug linked list manipulation" 1229 depends on DEBUG_KERNEL 1230 help 1231 Enable this to turn on extended checks in the linked-list 1232 walking routines. 1233 1234 If unsure, say N. 1235 1236config DEBUG_PI_LIST 1237 bool "Debug priority linked list manipulation" 1238 depends on DEBUG_KERNEL 1239 help 1240 Enable this to turn on extended checks in the priority-ordered 1241 linked-list (plist) walking routines. This checks the entire 1242 list multiple times during each manipulation. 1243 1244 If unsure, say N. 1245 1246config DEBUG_SG 1247 bool "Debug SG table operations" 1248 depends on DEBUG_KERNEL 1249 help 1250 Enable this to turn on checks on scatter-gather tables. This can 1251 help find problems with drivers that do not properly initialize 1252 their sg tables. 1253 1254 If unsure, say N. 1255 1256config DEBUG_NOTIFIERS 1257 bool "Debug notifier call chains" 1258 depends on DEBUG_KERNEL 1259 help 1260 Enable this to turn on sanity checking for notifier call chains. 1261 This is most useful for kernel developers to make sure that 1262 modules properly unregister themselves from notifier chains. 1263 This is a relatively cheap check but if you care about maximum 1264 performance, say N. 1265 1266config DEBUG_CREDENTIALS 1267 bool "Debug credential management" 1268 depends on DEBUG_KERNEL 1269 help 1270 Enable this to turn on some debug checking for credential 1271 management. The additional code keeps track of the number of 1272 pointers from task_structs to any given cred struct, and checks to 1273 see that this number never exceeds the usage count of the cred 1274 struct. 1275 1276 Furthermore, if SELinux is enabled, this also checks that the 1277 security pointer in the cred struct is never seen to be invalid. 1278 1279 If unsure, say N. 1280 1281menu "RCU Debugging" 1282 1283config PROVE_RCU 1284 def_bool PROVE_LOCKING 1285 1286config PROVE_RCU_REPEATEDLY 1287 bool "RCU debugging: don't disable PROVE_RCU on first splat" 1288 depends on PROVE_RCU 1289 default n 1290 help 1291 By itself, PROVE_RCU will disable checking upon issuing the 1292 first warning (or "splat"). This feature prevents such 1293 disabling, allowing multiple RCU-lockdep warnings to be printed 1294 on a single reboot. 1295 1296 Say Y to allow multiple RCU-lockdep warnings per boot. 1297 1298 Say N if you are unsure. 1299 1300config SPARSE_RCU_POINTER 1301 bool "RCU debugging: sparse-based checks for pointer usage" 1302 default n 1303 help 1304 This feature enables the __rcu sparse annotation for 1305 RCU-protected pointers. This annotation will cause sparse 1306 to flag any non-RCU used of annotated pointers. This can be 1307 helpful when debugging RCU usage. Please note that this feature 1308 is not intended to enforce code cleanliness; it is instead merely 1309 a debugging aid. 1310 1311 Say Y to make sparse flag questionable use of RCU-protected pointers 1312 1313 Say N if you are unsure. 1314 1315config TORTURE_TEST 1316 tristate 1317 default n 1318 1319config RCU_PERF_TEST 1320 tristate "performance tests for RCU" 1321 depends on DEBUG_KERNEL 1322 select TORTURE_TEST 1323 select SRCU 1324 select TASKS_RCU 1325 default n 1326 help 1327 This option provides a kernel module that runs performance 1328 tests on the RCU infrastructure. The kernel module may be built 1329 after the fact on the running kernel to be tested, if desired. 1330 1331 Say Y here if you want RCU performance tests to be built into 1332 the kernel. 1333 Say M if you want the RCU performance tests to build as a module. 1334 Say N if you are unsure. 1335 1336config RCU_TORTURE_TEST 1337 tristate "torture tests for RCU" 1338 depends on DEBUG_KERNEL 1339 select TORTURE_TEST 1340 select SRCU 1341 select TASKS_RCU 1342 default n 1343 help 1344 This option provides a kernel module that runs torture tests 1345 on the RCU infrastructure. The kernel module may be built 1346 after the fact on the running kernel to be tested, if desired. 1347 1348 Say Y here if you want RCU torture tests to be built into 1349 the kernel. 1350 Say M if you want the RCU torture tests to build as a module. 1351 Say N if you are unsure. 1352 1353config RCU_TORTURE_TEST_SLOW_PREINIT 1354 bool "Slow down RCU grace-period pre-initialization to expose races" 1355 depends on RCU_TORTURE_TEST 1356 help 1357 This option delays grace-period pre-initialization (the 1358 propagation of CPU-hotplug changes up the rcu_node combining 1359 tree) for a few jiffies between initializing each pair of 1360 consecutive rcu_node structures. This helps to expose races 1361 involving grace-period pre-initialization, in other words, it 1362 makes your kernel less stable. It can also greatly increase 1363 grace-period latency, especially on systems with large numbers 1364 of CPUs. This is useful when torture-testing RCU, but in 1365 almost no other circumstance. 1366 1367 Say Y here if you want your system to crash and hang more often. 1368 Say N if you want a sane system. 1369 1370config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY 1371 int "How much to slow down RCU grace-period pre-initialization" 1372 range 0 5 1373 default 3 1374 depends on RCU_TORTURE_TEST_SLOW_PREINIT 1375 help 1376 This option specifies the number of jiffies to wait between 1377 each rcu_node structure pre-initialization step. 1378 1379config RCU_TORTURE_TEST_SLOW_INIT 1380 bool "Slow down RCU grace-period initialization to expose races" 1381 depends on RCU_TORTURE_TEST 1382 help 1383 This option delays grace-period initialization for a few 1384 jiffies between initializing each pair of consecutive 1385 rcu_node structures. This helps to expose races involving 1386 grace-period initialization, in other words, it makes your 1387 kernel less stable. It can also greatly increase grace-period 1388 latency, especially on systems with large numbers of CPUs. 1389 This is useful when torture-testing RCU, but in almost no 1390 other circumstance. 1391 1392 Say Y here if you want your system to crash and hang more often. 1393 Say N if you want a sane system. 1394 1395config RCU_TORTURE_TEST_SLOW_INIT_DELAY 1396 int "How much to slow down RCU grace-period initialization" 1397 range 0 5 1398 default 3 1399 depends on RCU_TORTURE_TEST_SLOW_INIT 1400 help 1401 This option specifies the number of jiffies to wait between 1402 each rcu_node structure initialization. 1403 1404config RCU_TORTURE_TEST_SLOW_CLEANUP 1405 bool "Slow down RCU grace-period cleanup to expose races" 1406 depends on RCU_TORTURE_TEST 1407 help 1408 This option delays grace-period cleanup for a few jiffies 1409 between cleaning up each pair of consecutive rcu_node 1410 structures. This helps to expose races involving grace-period 1411 cleanup, in other words, it makes your kernel less stable. 1412 It can also greatly increase grace-period latency, especially 1413 on systems with large numbers of CPUs. This is useful when 1414 torture-testing RCU, but in almost no other circumstance. 1415 1416 Say Y here if you want your system to crash and hang more often. 1417 Say N if you want a sane system. 1418 1419config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY 1420 int "How much to slow down RCU grace-period cleanup" 1421 range 0 5 1422 default 3 1423 depends on RCU_TORTURE_TEST_SLOW_CLEANUP 1424 help 1425 This option specifies the number of jiffies to wait between 1426 each rcu_node structure cleanup operation. 1427 1428config RCU_CPU_STALL_TIMEOUT 1429 int "RCU CPU stall timeout in seconds" 1430 depends on RCU_STALL_COMMON 1431 range 3 300 1432 default 21 1433 help 1434 If a given RCU grace period extends more than the specified 1435 number of seconds, a CPU stall warning is printed. If the 1436 RCU grace period persists, additional CPU stall warnings are 1437 printed at more widely spaced intervals. 1438 1439config RCU_TRACE 1440 bool "Enable tracing for RCU" 1441 depends on DEBUG_KERNEL 1442 select TRACE_CLOCK 1443 help 1444 This option provides tracing in RCU which presents stats 1445 in debugfs for debugging RCU implementation. 1446 1447 Say Y here if you want to enable RCU tracing 1448 Say N if you are unsure. 1449 1450config RCU_EQS_DEBUG 1451 bool "Provide debugging asserts for adding NO_HZ support to an arch" 1452 depends on DEBUG_KERNEL 1453 help 1454 This option provides consistency checks in RCU's handling of 1455 NO_HZ. These checks have proven quite helpful in detecting 1456 bugs in arch-specific NO_HZ code. 1457 1458 Say N here if you need ultimate kernel/user switch latencies 1459 Say Y if you are unsure 1460 1461endmenu # "RCU Debugging" 1462 1463config DEBUG_WQ_FORCE_RR_CPU 1464 bool "Force round-robin CPU selection for unbound work items" 1465 depends on DEBUG_KERNEL 1466 default n 1467 help 1468 Workqueue used to implicitly guarantee that work items queued 1469 without explicit CPU specified are put on the local CPU. This 1470 guarantee is no longer true and while local CPU is still 1471 preferred work items may be put on foreign CPUs. Kernel 1472 parameter "workqueue.debug_force_rr_cpu" is added to force 1473 round-robin CPU selection to flush out usages which depend on the 1474 now broken guarantee. This config option enables the debug 1475 feature by default. When enabled, memory and cache locality will 1476 be impacted. 1477 1478config DEBUG_BLOCK_EXT_DEVT 1479 bool "Force extended block device numbers and spread them" 1480 depends on DEBUG_KERNEL 1481 depends on BLOCK 1482 default n 1483 help 1484 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1485 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1486 YOU ARE DOING. Distros, please enable this and fix whatever 1487 is broken. 1488 1489 Conventionally, block device numbers are allocated from 1490 predetermined contiguous area. However, extended block area 1491 may introduce non-contiguous block device numbers. This 1492 option forces most block device numbers to be allocated from 1493 the extended space and spreads them to discover kernel or 1494 userland code paths which assume predetermined contiguous 1495 device number allocation. 1496 1497 Note that turning on this debug option shuffles all the 1498 device numbers for all IDE and SCSI devices including libata 1499 ones, so root partition specified using device number 1500 directly (via rdev or root=MAJ:MIN) won't work anymore. 1501 Textual device names (root=/dev/sdXn) will continue to work. 1502 1503 Say N if you are unsure. 1504 1505config CPU_HOTPLUG_STATE_CONTROL 1506 bool "Enable CPU hotplug state control" 1507 depends on DEBUG_KERNEL 1508 depends on HOTPLUG_CPU 1509 default n 1510 help 1511 Allows to write steps between "offline" and "online" to the CPUs 1512 sysfs target file so states can be stepped granular. This is a debug 1513 option for now as the hotplug machinery cannot be stopped and 1514 restarted at arbitrary points yet. 1515 1516 Say N if your are unsure. 1517 1518config NOTIFIER_ERROR_INJECTION 1519 tristate "Notifier error injection" 1520 depends on DEBUG_KERNEL 1521 select DEBUG_FS 1522 help 1523 This option provides the ability to inject artificial errors to 1524 specified notifier chain callbacks. It is useful to test the error 1525 handling of notifier call chain failures. 1526 1527 Say N if unsure. 1528 1529config CPU_NOTIFIER_ERROR_INJECT 1530 tristate "CPU notifier error injection module" 1531 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION 1532 help 1533 This option provides a kernel module that can be used to test 1534 the error handling of the cpu notifiers by injecting artificial 1535 errors to CPU notifier chain callbacks. It is controlled through 1536 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu 1537 1538 If the notifier call chain should be failed with some events 1539 notified, write the error code to "actions/<notifier event>/error". 1540 1541 Example: Inject CPU offline error (-1 == -EPERM) 1542 1543 # cd /sys/kernel/debug/notifier-error-inject/cpu 1544 # echo -1 > actions/CPU_DOWN_PREPARE/error 1545 # echo 0 > /sys/devices/system/cpu/cpu1/online 1546 bash: echo: write error: Operation not permitted 1547 1548 To compile this code as a module, choose M here: the module will 1549 be called cpu-notifier-error-inject. 1550 1551 If unsure, say N. 1552 1553config PM_NOTIFIER_ERROR_INJECT 1554 tristate "PM notifier error injection module" 1555 depends on PM && NOTIFIER_ERROR_INJECTION 1556 default m if PM_DEBUG 1557 help 1558 This option provides the ability to inject artificial errors to 1559 PM notifier chain callbacks. It is controlled through debugfs 1560 interface /sys/kernel/debug/notifier-error-inject/pm 1561 1562 If the notifier call chain should be failed with some events 1563 notified, write the error code to "actions/<notifier event>/error". 1564 1565 Example: Inject PM suspend error (-12 = -ENOMEM) 1566 1567 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1568 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1569 # echo mem > /sys/power/state 1570 bash: echo: write error: Cannot allocate memory 1571 1572 To compile this code as a module, choose M here: the module will 1573 be called pm-notifier-error-inject. 1574 1575 If unsure, say N. 1576 1577config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1578 tristate "OF reconfig notifier error injection module" 1579 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1580 help 1581 This option provides the ability to inject artificial errors to 1582 OF reconfig notifier chain callbacks. It is controlled 1583 through debugfs interface under 1584 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1585 1586 If the notifier call chain should be failed with some events 1587 notified, write the error code to "actions/<notifier event>/error". 1588 1589 To compile this code as a module, choose M here: the module will 1590 be called of-reconfig-notifier-error-inject. 1591 1592 If unsure, say N. 1593 1594config NETDEV_NOTIFIER_ERROR_INJECT 1595 tristate "Netdev notifier error injection module" 1596 depends on NET && NOTIFIER_ERROR_INJECTION 1597 help 1598 This option provides the ability to inject artificial errors to 1599 netdevice notifier chain callbacks. It is controlled through debugfs 1600 interface /sys/kernel/debug/notifier-error-inject/netdev 1601 1602 If the notifier call chain should be failed with some events 1603 notified, write the error code to "actions/<notifier event>/error". 1604 1605 Example: Inject netdevice mtu change error (-22 = -EINVAL) 1606 1607 # cd /sys/kernel/debug/notifier-error-inject/netdev 1608 # echo -22 > actions/NETDEV_CHANGEMTU/error 1609 # ip link set eth0 mtu 1024 1610 RTNETLINK answers: Invalid argument 1611 1612 To compile this code as a module, choose M here: the module will 1613 be called netdev-notifier-error-inject. 1614 1615 If unsure, say N. 1616 1617config FAULT_INJECTION 1618 bool "Fault-injection framework" 1619 depends on DEBUG_KERNEL 1620 help 1621 Provide fault-injection framework. 1622 For more details, see Documentation/fault-injection/. 1623 1624config FAILSLAB 1625 bool "Fault-injection capability for kmalloc" 1626 depends on FAULT_INJECTION 1627 depends on SLAB || SLUB 1628 help 1629 Provide fault-injection capability for kmalloc. 1630 1631config FAIL_PAGE_ALLOC 1632 bool "Fault-injection capabilitiy for alloc_pages()" 1633 depends on FAULT_INJECTION 1634 help 1635 Provide fault-injection capability for alloc_pages(). 1636 1637config FAIL_MAKE_REQUEST 1638 bool "Fault-injection capability for disk IO" 1639 depends on FAULT_INJECTION && BLOCK 1640 help 1641 Provide fault-injection capability for disk IO. 1642 1643config FAIL_IO_TIMEOUT 1644 bool "Fault-injection capability for faking disk interrupts" 1645 depends on FAULT_INJECTION && BLOCK 1646 help 1647 Provide fault-injection capability on end IO handling. This 1648 will make the block layer "forget" an interrupt as configured, 1649 thus exercising the error handling. 1650 1651 Only works with drivers that use the generic timeout handling, 1652 for others it wont do anything. 1653 1654config FAIL_MMC_REQUEST 1655 bool "Fault-injection capability for MMC IO" 1656 depends on FAULT_INJECTION_DEBUG_FS && MMC 1657 help 1658 Provide fault-injection capability for MMC IO. 1659 This will make the mmc core return data errors. This is 1660 useful to test the error handling in the mmc block device 1661 and to test how the mmc host driver handles retries from 1662 the block device. 1663 1664config FAIL_FUTEX 1665 bool "Fault-injection capability for futexes" 1666 select DEBUG_FS 1667 depends on FAULT_INJECTION && FUTEX 1668 help 1669 Provide fault-injection capability for futexes. 1670 1671config FAULT_INJECTION_DEBUG_FS 1672 bool "Debugfs entries for fault-injection capabilities" 1673 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1674 help 1675 Enable configuration of fault-injection capabilities via debugfs. 1676 1677config FAULT_INJECTION_STACKTRACE_FILTER 1678 bool "stacktrace filter for fault-injection capabilities" 1679 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1680 depends on !X86_64 1681 select STACKTRACE 1682 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE 1683 help 1684 Provide stacktrace filter for fault-injection capabilities 1685 1686config LATENCYTOP 1687 bool "Latency measuring infrastructure" 1688 depends on DEBUG_KERNEL 1689 depends on STACKTRACE_SUPPORT 1690 depends on PROC_FS 1691 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC 1692 select KALLSYMS 1693 select KALLSYMS_ALL 1694 select STACKTRACE 1695 select SCHEDSTATS 1696 select SCHED_DEBUG 1697 help 1698 Enable this option if you want to use the LatencyTOP tool 1699 to find out which userspace is blocking on what kernel operations. 1700 1701source kernel/trace/Kconfig 1702 1703menu "Runtime Testing" 1704 1705config LKDTM 1706 tristate "Linux Kernel Dump Test Tool Module" 1707 depends on DEBUG_FS 1708 depends on BLOCK 1709 default n 1710 help 1711 This module enables testing of the different dumping mechanisms by 1712 inducing system failures at predefined crash points. 1713 If you don't need it: say N 1714 Choose M here to compile this code as a module. The module will be 1715 called lkdtm. 1716 1717 Documentation on how to use the module can be found in 1718 Documentation/fault-injection/provoke-crashes.txt 1719 1720config TEST_LIST_SORT 1721 bool "Linked list sorting test" 1722 depends on DEBUG_KERNEL 1723 help 1724 Enable this to turn on 'list_sort()' function test. This test is 1725 executed only once during system boot, so affects only boot time. 1726 1727 If unsure, say N. 1728 1729config KPROBES_SANITY_TEST 1730 bool "Kprobes sanity tests" 1731 depends on DEBUG_KERNEL 1732 depends on KPROBES 1733 default n 1734 help 1735 This option provides for testing basic kprobes functionality on 1736 boot. A sample kprobe, jprobe and kretprobe are inserted and 1737 verified for functionality. 1738 1739 Say N if you are unsure. 1740 1741config BACKTRACE_SELF_TEST 1742 tristate "Self test for the backtrace code" 1743 depends on DEBUG_KERNEL 1744 default n 1745 help 1746 This option provides a kernel module that can be used to test 1747 the kernel stack backtrace code. This option is not useful 1748 for distributions or general kernels, but only for kernel 1749 developers working on architecture code. 1750 1751 Note that if you want to also test saved backtraces, you will 1752 have to enable STACKTRACE as well. 1753 1754 Say N if you are unsure. 1755 1756config RBTREE_TEST 1757 tristate "Red-Black tree test" 1758 depends on DEBUG_KERNEL 1759 help 1760 A benchmark measuring the performance of the rbtree library. 1761 Also includes rbtree invariant checks. 1762 1763config INTERVAL_TREE_TEST 1764 tristate "Interval tree test" 1765 depends on m && DEBUG_KERNEL 1766 select INTERVAL_TREE 1767 help 1768 A benchmark measuring the performance of the interval tree library 1769 1770config PERCPU_TEST 1771 tristate "Per cpu operations test" 1772 depends on m && DEBUG_KERNEL 1773 help 1774 Enable this option to build test module which validates per-cpu 1775 operations. 1776 1777 If unsure, say N. 1778 1779config ATOMIC64_SELFTEST 1780 bool "Perform an atomic64_t self-test at boot" 1781 help 1782 Enable this option to test the atomic64_t functions at boot. 1783 1784 If unsure, say N. 1785 1786config ASYNC_RAID6_TEST 1787 tristate "Self test for hardware accelerated raid6 recovery" 1788 depends on ASYNC_RAID6_RECOV 1789 select ASYNC_MEMCPY 1790 ---help--- 1791 This is a one-shot self test that permutes through the 1792 recovery of all the possible two disk failure scenarios for a 1793 N-disk array. Recovery is performed with the asynchronous 1794 raid6 recovery routines, and will optionally use an offload 1795 engine if one is available. 1796 1797 If unsure, say N. 1798 1799config TEST_HEXDUMP 1800 tristate "Test functions located in the hexdump module at runtime" 1801 1802config TEST_STRING_HELPERS 1803 tristate "Test functions located in the string_helpers module at runtime" 1804 1805config TEST_KSTRTOX 1806 tristate "Test kstrto*() family of functions at runtime" 1807 1808config TEST_PRINTF 1809 tristate "Test printf() family of functions at runtime" 1810 1811config TEST_BITMAP 1812 tristate "Test bitmap_*() family of functions at runtime" 1813 default n 1814 help 1815 Enable this option to test the bitmap functions at boot. 1816 1817 If unsure, say N. 1818 1819config TEST_UUID 1820 tristate "Test functions located in the uuid module at runtime" 1821 1822config TEST_RHASHTABLE 1823 tristate "Perform selftest on resizable hash table" 1824 default n 1825 help 1826 Enable this option to test the rhashtable functions at boot. 1827 1828 If unsure, say N. 1829 1830config TEST_HASH 1831 tristate "Perform selftest on hash functions" 1832 default n 1833 help 1834 Enable this option to test the kernel's integer (<linux/hash,h>) 1835 and string (<linux/stringhash.h>) hash functions on boot 1836 (or module load). 1837 1838 This is intended to help people writing architecture-specific 1839 optimized versions. If unsure, say N. 1840 1841endmenu # runtime tests 1842 1843config PROVIDE_OHCI1394_DMA_INIT 1844 bool "Remote debugging over FireWire early on boot" 1845 depends on PCI && X86 1846 help 1847 If you want to debug problems which hang or crash the kernel early 1848 on boot and the crashing machine has a FireWire port, you can use 1849 this feature to remotely access the memory of the crashed machine 1850 over FireWire. This employs remote DMA as part of the OHCI1394 1851 specification which is now the standard for FireWire controllers. 1852 1853 With remote DMA, you can monitor the printk buffer remotely using 1854 firescope and access all memory below 4GB using fireproxy from gdb. 1855 Even controlling a kernel debugger is possible using remote DMA. 1856 1857 Usage: 1858 1859 If ohci1394_dma=early is used as boot parameter, it will initialize 1860 all OHCI1394 controllers which are found in the PCI config space. 1861 1862 As all changes to the FireWire bus such as enabling and disabling 1863 devices cause a bus reset and thereby disable remote DMA for all 1864 devices, be sure to have the cable plugged and FireWire enabled on 1865 the debugging host before booting the debug target for debugging. 1866 1867 This code (~1k) is freed after boot. By then, the firewire stack 1868 in charge of the OHCI-1394 controllers should be used instead. 1869 1870 See Documentation/debugging-via-ohci1394.txt for more information. 1871 1872config DMA_API_DEBUG 1873 bool "Enable debugging of DMA-API usage" 1874 depends on HAVE_DMA_API_DEBUG 1875 help 1876 Enable this option to debug the use of the DMA API by device drivers. 1877 With this option you will be able to detect common bugs in device 1878 drivers like double-freeing of DMA mappings or freeing mappings that 1879 were never allocated. 1880 1881 This also attempts to catch cases where a page owned by DMA is 1882 accessed by the cpu in a way that could cause data corruption. For 1883 example, this enables cow_user_page() to check that the source page is 1884 not undergoing DMA. 1885 1886 This option causes a performance degradation. Use only if you want to 1887 debug device drivers and dma interactions. 1888 1889 If unsure, say N. 1890 1891config TEST_LKM 1892 tristate "Test module loading with 'hello world' module" 1893 default n 1894 depends on m 1895 help 1896 This builds the "test_module" module that emits "Hello, world" 1897 on printk when loaded. It is designed to be used for basic 1898 evaluation of the module loading subsystem (for example when 1899 validating module verification). It lacks any extra dependencies, 1900 and will not normally be loaded by the system unless explicitly 1901 requested by name. 1902 1903 If unsure, say N. 1904 1905config TEST_USER_COPY 1906 tristate "Test user/kernel boundary protections" 1907 default n 1908 depends on m 1909 help 1910 This builds the "test_user_copy" module that runs sanity checks 1911 on the copy_to/from_user infrastructure, making sure basic 1912 user/kernel boundary testing is working. If it fails to load, 1913 a regression has been detected in the user/kernel memory boundary 1914 protections. 1915 1916 If unsure, say N. 1917 1918config TEST_BPF 1919 tristate "Test BPF filter functionality" 1920 default n 1921 depends on m && NET 1922 help 1923 This builds the "test_bpf" module that runs various test vectors 1924 against the BPF interpreter or BPF JIT compiler depending on the 1925 current setting. This is in particular useful for BPF JIT compiler 1926 development, but also to run regression tests against changes in 1927 the interpreter code. It also enables test stubs for eBPF maps and 1928 verifier used by user space verifier testsuite. 1929 1930 If unsure, say N. 1931 1932config TEST_FIRMWARE 1933 tristate "Test firmware loading via userspace interface" 1934 default n 1935 depends on FW_LOADER 1936 help 1937 This builds the "test_firmware" module that creates a userspace 1938 interface for testing firmware loading. This can be used to 1939 control the triggering of firmware loading without needing an 1940 actual firmware-using device. The contents can be rechecked by 1941 userspace. 1942 1943 If unsure, say N. 1944 1945config TEST_UDELAY 1946 tristate "udelay test driver" 1947 default n 1948 help 1949 This builds the "udelay_test" module that helps to make sure 1950 that udelay() is working properly. 1951 1952 If unsure, say N. 1953 1954config MEMTEST 1955 bool "Memtest" 1956 depends on HAVE_MEMBLOCK 1957 ---help--- 1958 This option adds a kernel parameter 'memtest', which allows memtest 1959 to be set. 1960 memtest=0, mean disabled; -- default 1961 memtest=1, mean do 1 test pattern; 1962 ... 1963 memtest=17, mean do 17 test patterns. 1964 If you are unsure how to answer this question, answer N. 1965 1966config TEST_STATIC_KEYS 1967 tristate "Test static keys" 1968 default n 1969 depends on m 1970 help 1971 Test the static key interfaces. 1972 1973 If unsure, say N. 1974 1975source "samples/Kconfig" 1976 1977source "lib/Kconfig.kgdb" 1978 1979source "lib/Kconfig.ubsan" 1980 1981config ARCH_HAS_DEVMEM_IS_ALLOWED 1982 bool 1983 1984config STRICT_DEVMEM 1985 bool "Filter access to /dev/mem" 1986 depends on MMU 1987 depends on ARCH_HAS_DEVMEM_IS_ALLOWED 1988 default y if TILE || PPC 1989 ---help--- 1990 If this option is disabled, you allow userspace (root) access to all 1991 of memory, including kernel and userspace memory. Accidental 1992 access to this is obviously disastrous, but specific access can 1993 be used by people debugging the kernel. Note that with PAT support 1994 enabled, even in this case there are restrictions on /dev/mem 1995 use due to the cache aliasing requirements. 1996 1997 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem 1998 file only allows userspace access to PCI space and the BIOS code and 1999 data regions. This is sufficient for dosemu and X and all common 2000 users of /dev/mem. 2001 2002 If in doubt, say Y. 2003 2004config IO_STRICT_DEVMEM 2005 bool "Filter I/O access to /dev/mem" 2006 depends on STRICT_DEVMEM 2007 ---help--- 2008 If this option is disabled, you allow userspace (root) access to all 2009 io-memory regardless of whether a driver is actively using that 2010 range. Accidental access to this is obviously disastrous, but 2011 specific access can be used by people debugging kernel drivers. 2012 2013 If this option is switched on, the /dev/mem file only allows 2014 userspace access to *idle* io-memory ranges (see /proc/iomem) This 2015 may break traditional users of /dev/mem (dosemu, legacy X, etc...) 2016 if the driver using a given range cannot be disabled. 2017 2018 If in doubt, say Y. 2019